Hello,
Thank you for your query at DoctorSpring.com
I understand your concern.
There are a lot of indirect causes of loss of attention or difficulty in focussing. If it is associated with mild dizziness it could be low hemoglobin ( anemia ), low vitamin b 12 levels, hypotension, hypoglycemia, or stress.
In adults commonest cause of loss of attention is Adult ADHD, but that is more of a chronic manifestation and not sudden.
Did you get your blood work done recently? If so do share the reports.
Feel free to discuss further,
Regards.